topic Re: tape backups in Operating System - OpenVMS

tape backups

nipun_2 — Thu, 29 Sep 2005 09:04:07 GMT

Hi,
I have 3 node clustered system with a two disks (DATA1 & DATA2)

DATA1 and DATA2 are the volume set for the combined hard drives.

We currently perfrom a single backup ("primary backup" which "moves" the data to the tape.

But this might be a problem in future if the tape get's damaged.

To prevent this I am thinking of performing a periodic backup of all the data on the both disks.

These are my questions:
1) I have SDLT320 Drive so each disk will be 320GB however the data on both the disks would be more than that.
2) I would like to somethign along the lines of incremental backup. So if I backup every 2 weeks or month, I don't want to back up the previous data. Also if I mark a folder/files as backed up then it would not allow the "primary backup".

Any suggestion or comments would be useful. On the basis of these I will choose the right qualifiers and post them here.

Thanks in advance.
Nipun

Re: tape backups

Joseph Huber_1 — Thu, 29 Sep 2005 09:23:51 GMT

1) what is Your problem: if the disk to backup does not fit on 1 tape cartridge, then BACKUP will ask for a continuation tape.

2) Usually the sequence is:
full backup: /IMAGE/RECORD disk: tape:/save

every 2 weeks incremental: /RECORD disk:[000000...]/SINCE=BACKUP

Why should that not allow the full backup ?

Re: tape backups

Uwe Zessin — Thu, 29 Sep 2005 09:26:59 GMT

Hello Nipun,
you wrote: "DATA1 and DATA2 are the volume set".

Do I undestand correctly that you used MOUNT/BIND to create an OpenVMS volume set?

For incremental backups you can use a combination of BACKUP /RECORD /SINCE=BACKUP, but I prefer a 'differential backup' (pick up all files since the last full backup), unless much data changes.

The reason is that this only needs two tape operations:
- restore the last image
- restore the last differential

You can still pick up single files from backup between the full backup and the last differential.

Re: tape backups

Willem Grooters — Thu, 29 Sep 2005 09:37:54 GMT

First to keep in mind that BACKUP is no goal in itself. It's a tool that allows you to RESTORE.
having said that - Incremental backup is handy but if you lose a disk completely, you'll need the full backup and all incrementals. One tape lost = data loss. It may, or may be not fatal to your business.
This is particular true for databases. Loss of a single tape may cause loss of data if later tapes do not hold that file (and it may cause inconsistence). Loss of a database log file however renders all subsequent logfiles unusable, so you may end up with a consistent database where a LOT of data is lost - completely - and it cannot be restored safely.
So you'd better be sure to have your tapes correct. The best way to etst is to restore a full backup including all following incrementals on an empty disk.
There are several schemas for backup - it's worth specning some time to do some calculation on backup- and restore times.

Use BACKUP/IMAGE for a full backup.

Willem

Re: tape backups

Joseph Huber_1 — Thu, 29 Sep 2005 09:42:45 GMT

Or does Your question 1) mean: do I have a problem to restore the backup of the volume-set, if the disk to restore to is smaller than the original volume-set ?

Yes there will be a problem, and backup will not be able to restore everything.

Re: tape backups

Lawrence Czlapinski — Thu, 29 Sep 2005 11:42:38 GMT

Nipun: How often do you do a full backup?
Lawrence

Re: tape backups

Ian Miller. — Fri, 30 Sep 2005 04:51:52 GMT

Re: tape backups

nipun_2 — Fri, 30 Sep 2005 10:18:23 GMT

Hello everyone,
I am currently reading through your notes as well as the documentation notes provided by Ian.

Uwe's suggestion for differential backup seems to be suitable. However, I still need to read more on the backup strategy. Once I go through it I will ask you guys again.

Maybe my explanation below will help answer some of the questions posted.
My basic goal for this entire process:
To have redundant data on two tapes.

Current idea is people have their own accounts and they back up (which also moves ) their data to tape. Thus at one time there is only one copy of the data either on hard drive or tape.

Note: As I mentioned earlier I will go through the documentation and try to be more specific.

Re: tape backups

Lawrence Czlapinski — Fri, 30 Sep 2005 11:42:11 GMT

Nipun:
1. You can do as many full backups as you want. It backups up everything. Your "primary backup" should be a full backup. We do at least weekly full backups and on some machines daily full backups. Remember to send a full backup offsite. We send the most recent monthly full backup offsite.
2. Users shouldn't do a BACKUP/RECORD. So that shouldn't interfere with your incremental backups.
3. Backup doesn't delete files. So you normally have the files on both disk and on tape.
4. I would also do cumulative incremental BACKUPs rather than incremental BACKUP/RECORD as previously suggested. If you do incremental BACKUP/RECORD and you lose a disk and the tape with those files goes bad for normal wear and tear or otherwise you lose whatever files changed that were on that tape. If you only do incremental BACKUP every 2 weeks or month, you could lose up to a month's worth of changes. A tape is more likely to go bad as it ages but you could always get hit with a lemon (one that fails unusually early). Incremental backups should be done at least every weekday. Do you want to explain to someone that you lost up to a months worth of data. With cumulative incremental BACKUP, you would only have a problem if the file was only on the most recent tape and that tape went bad. You could make two (or more) cumulative incremental backup tapes if you want. You could store a cumulative incremental backup tape offsite.
5. We also do special quarterly and half year tape BACKUPs of some DATABASE data that will be removed after the data is backed up.
Lawrence

Re: tape backups

Uwe Zessin — Fri, 30 Sep 2005 12:14:13 GMT

Well, of course one would not use /RECORD on a differential ("cumulative incremental") backup. Sorry, I thought that was obvious ;-)

Re: tape backups

nipun_2 — Mon, 21 Nov 2005 09:22:00 GMT

Thank you all. Esp lawrence for the detailed reply.

Nipun